As we said, the teachers at the sandy hook elementary school had been trained to react to a threat never expecting to use that training. Abc's amy robach is with us now and she tells us what the training was and exactly what they did. Amy? That's right, we're here at danbury hospital where the medical staff toldis they thought it must have been a lot like 911 because they had their entire staff waiting here to receive the injured. Only three arrived. The death count unimaginable, but as you mentioned, so many people are attributing that number to the heroic acts of teachers. If it weren't for their bravery, many in the community believe that number would have been even higher. Reporter: For the nearly 700 students who attend sandy hook elementary school, it is the teachers' words they follow day in and day out. Today, those words might have just saved their life. His teacher went and checked, locked and closed the door. They went into a corner until they were recovered by police. The teacher put them in the corner and they weren't allowed to move until the police came. Rita has been serving pizza there for more than 30 years. They're all heroes. It doesn't sound that the teachers did everything humanly possible, down to risking their own lives to protect the children in this connecticut school. Elementary schools across the country have been preparing for lock down drills, evacuations, and other security measures since columbine. Reporter: Just this year, sandy hook put into place a security plan. Making it mandatory for visitors to ring a door bell. And if staff didn't recognize the visitor, he or she needed to present picture i.D., Sign in and only then would be let into Eefr time we went to the school, you had to press the button, they'd ask who you are to come in. I don't know how anybody could walk in. This tweet from teachers. My cousin is the assistant principal at the newtown shooting and was shoot twice. This face telling it all, this woman's sister, one of those teachers inside the school, her whereabouts unknown. There's no words that I could come u you don't know the details of the violence and you can't do anything to help them or protect them. That is a powerless and terrifying experience. Reporter: Speaking of powerless, I just spoke to one of the doctors here who was at danbury hospital when they received the initial call multiple shots fired he amassed 80 doctors and nurses waiting to receive any potential victims and injured. Within the first ten minutes, they got those initial three injured and they were waiting for more. They were told as many as two dozen they would receive. Within 30 minutes when they didn't show up, that's twh they felt the gravity of the situation because they knew they weren't coming, they were at the school and would stay there forever. It was a very disturbing moment for all of them. They said they're still going to be dealing with this obviously for months and years to come. This community is forever changed. No one here hasn't been touched by this horrific tragedy.

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